You say tornado, I say ... tornadic squall?

Freya Petersen

As gusts of wind began forming tight circular patterns around the Bundaberg area late yesterday, the existence – or otherwise – of tornados in Australia became a topic of heated debate.

Many Fairfax readers took exception to the use of the term, labelling it as an Americanisation and preferring the term "cyclone", "tornadic squall" or even "whirly-whirly".

The Australian Bureau of Meteorology, however, sanctions the use of the term, stating on its website that:

"While both tropical cyclones and tornadoes are atmospheric vortices, they have little in common. Tornadoes have diameters on the scale of hundreds of metres and are usually produced from a single thunderstorm. A tropical cyclone, however, has a diameter on the scale of hundreds of kilometres and contains many thunderstorms.

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"Tornadoes are primarily an over-land phenomena as solar heating of the land surface usually contributes toward the development of the thunderstorm that spawns the vortex (though over-water tornadoes have occurred). In contrast, tropical cyclones are purely an oceanic phenomena - they die out over-land due to a loss of a moisture source. Lastly, tropical cyclones have a lifetime that is measured in days, while tornadoes typically last on the scale of minutes."

The BoM's explanation of tornadoes goes on to describe the conditions needed to form one, including "an intense, sustained updraught; strong wind shear... and strong winds at cloud-top level".

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While taking no issue with the use of "tornado" specifically, one reader named Kate insisted that:

"There is no such thing as a 'mini-tornado' and the media needs to stop using it. 'Hurricane' and 'typhoon' are regionally specific names for a strong 'tropical cyclone'."

A road sign flies through the air as a tornado hits Moama. Picture: Jenna Natalizio

She's right there, according to the BoM, which adds that "hurricane" is used in the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E, while "typhoon" is used in the Northwest Pacific Ocean, west of the dateline.

Kate later adds that she holds a "Bachelor's degree in atmospheric science and a Masters thesis on tropical cyclone forecasting".

The suggestion that "tornadoes" might not exist in Australia prompted Lynne of Melbourne to comment:

"Really? My nephew had just stepped out onto the street in Bargara when the first 'non-tornado' hit today ... So far today: one of these figments of our imaginations at Bargara, two at Burnett Heads, another at Coonar, and one headed for Maryborough. I dread to think of the damage there might have been if we did get real tornadoes."

Neal, of Cairns, was less circumspect:

"'We don't have tornadoes in Australia'... What a load of rot. We do indeed. Though I suspect these ones started as water based systems (water spouts) due to the nth east feed and ran ashore. Conditions are perfect for them and they may not be the last with this low. For the record an entire street was smashed by a tornado in Townsville not long ago and another was filmed will inland on the Atherton tablelands last year.'

According to the Oxford Dictionary, the term stems from the mid-16th century definition, denoting "a violent thunderstorm of the tropical Atlantic Ocean," which perhaps comes from the Spanish tronada, or "thunderstorm".

One Australian expert who concurs with the use of the term tornado - and the BoM's description of how they form - is John Allen, a researcher at the University of Melbourne who has recently completed his PhD on the topic of severe thunderstorms in Australia.

"The word's been around for far longer than the Americans have been using it - it's been around in European records since the 1600s ... and there are examples even further back," he told Fairfax Media.

"London had one in the 1600s, there's examples on the European continent quite regularly.

"If they're a rapidly turning area of wind to a cloud - sometimes with a condensation funnel, sometimes not - they're a tornado. It doesn't matter how they form - they're still a tornado."

However, Mr Allen warns that the prefix "mini" is probably "inappropriate" when used in connection with a tornado, warning that it may downplay the seriousness of the weather event.

"There are examples of people being killed quite regularly in the Australian records," he said, using the examples of Nhill in Western Victoria in the 1897 and Nevertire in western NSW, destroyed at the turn of the century by a tornado.